Huh??

[Wallythacker]

On my last fill I was amazed to only take on about 29l for about 505 kms.

I was shocked that the blinking did not start until about 480 km. That's a near record for me.

What is so unusual about that fill? Well, for most of the tank I was hauling my 4x8 AL trailer! And...I was booking it, driving a little over 70 mph which I rarely do and have only ever done once or twice with a trailer.

Color me surprised.

[MetroMPG]

Short fill? You'll know for sure next time.

Or... did you have a massive tailwind on that trip?

[Wallythacker]

Short fill? You'll know for sure next time.

Or... did you have a massive tailwind on that trip?

nope, current fuel use indicates a full fill. It was a calm day

[sunbeam]

I only measure the fuel economy using fill to fill receipts ie. Fill tank, drive a distance, fill again.

The cars measurements are all subject to error, this to me is the most accurate way.

It could be random variance, it could be measurement error, it could be non-ethanol gas vs ethanol gas (up to 15% difference in fuel economy).

[7milesout]

I estimate that the information display mpg is off optimistically by around 7.5%. Comes out real close when I do the math.

To eyeball that, if the display says 44 mpg (for example), I multiply (in my mind) 44 by 7, and get 28X (two hundred eighty something) or 29X (two hundred ninety something). It's actually 30X (three hundred something, but I'm conveying what I quickly "estimate." Then I know to pull about 3 mpg (29X, move the decimal 2 places to the left = 2.9X ... so more or less 3) off the 44 mpg on the display, and effectively I got about 41 mpg. I eyeball that, like that, then actually do the math on miles per gallon filled. Comes out very close eyeballing it like that.